Locking mailbox



FIG. 1 is a perspective view of a locking mailbox showing our new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a right side elevational view with the left side being a mirror image thereof;

FIG. 5 is top view thereof; and,

FIG. 6 is a bottom view thereof.

The broken lines represent environmental structure and form no part of the claimed design. 

The ornamental design for a locking mailbox, as shown and described. 